1. Field of the Invention
A header pallet for the manufacture of a single offset notch on the end of the spigot of a concrete pipe to receive a sealing gasket during assembly of a pipe line.
2. Description of the Prior Art
It is common practice to make concrete pipe sections with a bell and spigot end utilizing a resilient packing ring or sealing gasket between the bell and spigot ends of interconnected pipe sections. In order to provide a retaining means for a sealing ring or gasket, it is common practice to provide an inwardly extending annular groove in the spigot end of the pipe sections.
Typically concrete pipe is produced by one of several molding methods, such as by centrifugal spinning or by the more common casting in vertical molds vibrated to compact the concrete or casting in fixed vertical molds with the compacting performed by a moving core. In the latter technique, it is also common practice to utilize some form of separate mold or former to make the ring receiving groove or channel in the spigot end of the pipe. The pipes are usually molded bell end down and spigot end up. These auxiliary molds or spigot groove formers are generally placed on top of the mold. There is a common problem encountered in this spigot groove forming in that in order to provide a smooth unbroken ring receiving groove in the finished pipe the groove forming member must necessarily be capable of being freed from the compacted partially set pipe without damage to the grrove it has formed and the adjacent pipe body. In order to overcome this problem various expedients have been proposed, for example, a resilient forming ring has been used which can be stretched radially after the molding and slipped off the pipe while in stretched condition.
Other expedients including a forming ring in segments which are separated for removal and to make the forming member as a spring type split ring which is initially sprung closed against the spigot for forming by an arrangement of screws or bolts and released to spring open for its removal.
U.S. Pat. No. 3,341,910 discloses an apparatus for forming concrete pipes including a removable profile ring to form the "O" ring chamber or recess commonly known in the industry.
U.S. Pat. No. 3,114,956 teaches the manufacture of concrete pipe to form the bell end and male end of the pipe accurately to facilitate the installation and joining of the pipe sections and to provide a dependable leak-proof seal at the joint. The abutment surface, the tapered surface and the gasket groove comprise the sides and bottom under precise dimension and concentricity so as to properly mate with the abutment surface and tapered bore of the bell end of the pipe so that the gasket forms a proper seal at the pipe joint. Ordinarily the concrete pipe sections are cast in a vertical position with the bell end down, the outer surface of the pipe being formed by the outer mold which rests on a suitable platform while the aggregate is dumped in at the top and the mold structure subjected to suitable vibration to compact the material. The bore of the pipe is formed and troweled smooth by the core element which rises up through the mold as the material is fed in above and around the core element which finally emerges from out of the upper end of the pipe. The male end of the pipe is formed by a specially constructed molding ring comprising a plurality of molding ring segments having radially disposed abutment ends when the segments are placed together. Each of the segments have the annular ring portion formed on the tapered bore surface thereof for forming the gasket groove in the pipe. The radially disposed surface of the ring forms the abutment surface on the upper end of the pipe while the radially disposed surface forms the clearance surface on the pipe. The exterior of the ring is formed with an outwardly downwardly sloping surface which matingly engages the tapered bore in the header ring so that downward pressure on the top surface of the header ring firmly and accurately locks the ring segments in position abutment contact at radially disposed abutment end parting lines to form a continuous rigid ring engaging the male end of the pipe. Suitable clearance is provided between the ring and the header for proper sealing and aligning action between the tapered surfaces. The functioning and operation of the structures are identical, except that in the latter group two segments are used instead of three segments. The assembled device is placed in the bore of the outer mold at the upper end thereof and initially supported on any suitable releasable means such as the pull pins carried in the outer mold. The top surface of the header ring is backed up by the thrust platen of the pipe making machine so that the upward thrust caused by the upward movement of the core element in forcing the concrete outwardly and upwardly against the ring segments is absorbed through the header ring to thereby automatically maintain the segments in tight aligned abutting contact through the operation of the tapered surfaces as described so that the greater the outward and upward forces against the segments, the tighter will be the tapered locking action thereon by the header ring. After the pipe has been cast, the operator partially rotates the assembly to improve the finish of the pipe and create a trowelled finish. Then the core element fully upwardly withdrawn and the thrust platen withdrawn, the cast pipe in the outer mold is moved from the machine to the curing area. The outer mold is then pulled upwardly from the cast pipe leaving the gasket groove forming device on top of the cast pipe. The following day, a screw driver or pinch bar is placed in the clearance groove to release the header ring from the segments whereupon the segments are moved radially away from the pipe leaving the complete perfectly formed male end of the pipe to set up and age.
U.S. Pat. No. 3,124,857 relates to the manufacure of concrete pipe and more particularly to improvements in the preparing of concrete pipe sections for interconnection. This is accomplished by providing a spigot groove former which consists basically of three (3) main parts namely, an L-shaped bottom ring supporting a plurality of supporting brackets, stoppers and a locating bracket, a removable top ring which is either rectangular or L-shaped, depending on the type of molding process as will be described and which is secured to the bottom ring through the supporting brackets by provide an annular space in which will slide the third element, namely a retractible middle ring. The retractible middle ring which can be rectangular, or preferably a U-shaped channel to maintain flexibility is split with the open ends connected by a toggle clamp arrangement. A plurality of stoppers and a locating lug are provided on the retractible ring which, in combination with the bottom and top rings make the retractible ring self-centering when closed by the toggle clamp. The interior faces of the bottom and top rings are machined so that they acurately form the spigot and offer support to the concrete when the middle ring is retracted. In use, the groove former is supported directly on the upper end of the pipe mold over the partially compacted pipe and the forming ring reduced in diameter by the toggle clamp to form the desired groove. When the concrete is fully compacted and set to a degree permitting removal of the mold, the toggle is opened forcing the retractible ring outwards until it contracts the stoppers provided on the bottom ring thus clearing the groove formed and permitting removal of the former as a unit.
U.S. Pat. No. 3,139,469 shows a method for forming machine-made concrete pipe with permanent sealing inserts to provide a premium joint comprising placing a plastic bell sealing insert on a bell pallet, securing an outside pipe forming jacket around the bell pallet so that the bell pallet is supported thereon, placing a rubber gasket in a groove on a plastic spigot sealing insert, positioning said spigot insert on a spigot pallet so that the gasket is received in a recess on the spigot pallet, positioning and securing the spigot to the outside pipe forming jacket and filling the pipe forming jacket with a no-slump concrete mix.
U.S. Pat. No. 4,522,669 discloses a method of manufacturing a combination mold portion and protective element from a flat cut blank material subject to dimensional changes and using said element to protect and form joint surfaces formed in a socket portion of a concrete pipe adapted to be connected to another pipe, comprising the steps of transporting at least one flat cut blank to a site where the concrete pipe is to be poured, forming at least one of the blanks into an annular shaped element by progressively feeding the blank along an inner annular peripheral surface of an annular shaping device, positioning the annular shaped mold portion element in relation to a pair of side mold portions and a bottom ring mold portion to define therewith a cavity forming said socket portion of the pipe, pouring concrete into the cavity to form the socket portion, the annular shaped mold portion element defining inner surfaces of the socket portion adapted to sealingly connect with another pipe and removing the side mold portions and bottom ring mold portion after the concrete has hardened, the annular shaped element being left intact in tight fitting engagement to protect inner surfaces of the socket portion against contact with water or soil during transportation and storage of the pipe. The mold includes an outer and inner portion in combination with a bottom ring. A sealing ring is embedded into the bell of the concrete pipe immediately adjacent a protective element removably secured to the bell portion by tape.
U.S. Pat. No. 2,559,296 teaches a composition pipe mold of the type having an inner mold section and a concentrically disposed outer mold section wherein each section is formed from metal plates and the ends of the metal plates are arranged in overlapping relationship and means for securing the ends of the outer mold section. The improvement comprising a bracket adjacent each free edge of the plate forming the inner mold section, a clamp engaging the brackets whereby the plate will be held in a substantially tubular form, an inclined guideway adjacent each free edge of the plate near the lower end thereof and a wedge element adapted to be lodged in the guideways to prevent the collapse of the plate when in tubular form.
Unfortunately the production and use of "O" ring grooves have significant limitations. Specifically such structures are difficult to produce, hard to repair damaged pipe and require lubrication in groove during pipe line assembly to prevent the "O" ring from moving out of the groove that could break the bell destroying the water integrity of the pipe line.
In contrast, a single offset notch formed on the spigot or grooveless pipe permits the use of a wide variety of sealing gaskets with more than one point of seal and a greater sealing area.
For example, flat profile gaskets may include multiple surfaces to hold and retain lubricant and distribute pressure load of gasket over an expanded area.
However, replacement of "O" ring groove headers or header pallets would be extremely expensive. Therefore, conversion of "O" ring header pallets to produce a single offset spigot notch with an inexpensive compressible part or structure is dictated without any change to the header. Thus present headers can be used and, if necessary, converted back to the original type with no wear or damage resulting. The system is convertible between a single offset spigot notch or "O" ring header.